Electrical service providers such as electrical utilities employ electricity meters to monitor energy consumption by customers (or other entities). Electricity meters track the amount of energy consumed by a load (e.g. the customer), typically measured in kilowatt-hours (“kwh”), at each customer's facility. The service provider uses the consumption information primarily for billing, but also for resource allocation planning and other purposes.
Electrical power is transmitted and delivered to load in many forms. For example, electrical power may be delivered as polyphase wye-connected or delta-connected power or as single phase power. Such various forms are known as service types. Different standard electricity meter types, known as meter forms, are used to measure the power consumption for the various service types. The commonly used meter forms in the United States include those designated as 2S, 3S, 5S, 45S, 6S, 36S, 9S, 16S, 12S and 25S meter forms, which are well known in the art.
Electrical service providers have historically billed for electrical service in arrears, using information stored within the electricity meter to determine the amount of each invoice. In a typical operation, the electricity meter stores a value representative of the amount of energy consumed in a mechanical or electronic accumulation register. From time to time, the electrical service provider obtains the value of the register and bills the customer accordingly. For example, a meter reader employed by the service provider may, each month, physically read the register value off of a meter display. The service provider then employs the obtained register value to determine the amount of electricity consumed over the month and bills the customer for the determined amount.
A problem with the above-described operation of electrical service providers arises from the fact that some customers are frequently delinquent in or, in default of, payments for electricity consumption. Because electrical service is billed in arrears, delinquent payments can result in significant losses for the service provider. In many cases, the utility must interrupt power to prevent additional losses. However, interrupting the delivery of electrical power has historically been an expensive and significant event. Typically, a technician must be dispatched to the customer's residence, or in the vicinity thereof, to physically disconnect the power. Accordingly, while the electrical service provider can justify physically disconnecting the power to the customer's facility after several months of default, physical disconnection is not practical in circumstances in which customers are merely delinquent, or can only pay portions of their bills. In particular, the cost and effort of sending a technician out to disconnect electrical service is wasted if the customer pays a day or two later, thereby requiring another service call to restore service.
One method of controlling losses associated with risk of non-payment is to require prepayment for services. In prepayment arrangements, customers use prepaid debit cards or credit cards to “purchase” energy in advance. When the purchased energy has been consumed, the electrical service is disconnected. Thus, the service provider is not exposed to extended periods of electrical service for which no payment may be provided. Another method of handling delinquent customers is to intermittently interrupt power to delinquent customers until the past due payments are made. Intermittent interruptions tend to reduce the amount of energy consumed by the delinquent payor, thus advantageously reducing utility provider losses while also reducing bills to the delinquent payor.
Each of the above methods, however, typically requires the ability to disconnect and/or reconnect the customer's power without a technician service call to the customer's location. For example, in a prepayment scenario, the service provider must have a method of disconnecting power once the prepaid amount of energy has been consumed. Similarly, the intermittent interruption technique requires frequent connection and disconnection of the electrical service.
One technique for automated or remote service disconnection is to employ a service switch device within an electricity meter. The service switch is a relay or other switching element that controllably disconnects and re-connects the utility power lines to the customer's feeder lines, thereby controllably interrupting power to the customer's facility. In some cases, the service switch is tripped by a remote device that communicates with the electricity meter circuitry through a modem, radio or the like. Alternatively, such as in the case of prepayment, the meter itself may be programmed to disconnect and reconnect electrical service under certain circumstances. In some situations, the meter may disconnect and restore electrical service through a combination of local programming and remote commands.
Thus, the inclusion of a service switch within a meter facilitates various methods and techniques for providing improved electrical service to parties despite poor payment records. Such methods and techniques advantageously do not require a permanent disconnection by a field technician.
The conveniences provided by a service switch also extend beyond use in connection with high-risk payors. For example, electrical energy rationing may be implemented using techniques enabled by the service switch. Moreover, service disconnect features are often employed within so-called “Smart Meters”. The term “Smart Meter” has been used to describe electricity metering systems that use a wide area network (WAN) or the like to enable communication and control over networks of meters. The WAN is used to communicate with “Smart Meters” for purposes of obtaining energy information and to operate the service switch. The WAN can also be used to reprogram the electricity meter. Communication with the “Smart Meter” is an essential element in managing the electrical power grid. An essential element of the “Smart Grid” is the “Smart Meter”.
An issue that arises with service switches, however, relates to the meter's handling of large current spikes, such that those associated with a lightning strike or other anomaly. While failure of the meter under such extreme conditions cannot always be avoided, it is also paramount that any failure under extreme high current conditions be as graceful as possible.
In the past service switches have been operated by motor-driven actuators. These actuators included spring loaded contacts that ensured a high current, low resistance coupling of the customer load to the power lines. In some cases, however, a high current event under some circumstances causes separation of the contacts of the power switch, resulting in an arc between the contacts. Arcs can cause undesirable failure modes in an electricity meter.
There is a need, therefore, for an arrangement for providing service disconnect in an electricity meter that provides increased protection against undesirable high current event failure modes.